There are three big problems with Gentoo Linux: first of all, most if not all Gentoo systems
are completely broken (missing or mismatched header files, broken compiler etc. are just the
tip of the iceberg); secondly, the Gentoo maintainer thinks it is a good idea to add broken
patches to the code; and lastly, it should be called Gentoo GNU/Linux.

For these reasons, it is impossible to support rxvt-unicode on Gentoo. Problems appearing on
Gentoo systems will usually simply be ignored unless they can be reproduced on non-Gentoo
systems.

My experience with gentoo so far is very good. For example I've learned in the last 4 months more about linux then in the last 5 years and even so everything that I need works fine and stable.
One (or THE) reason for me to go with gentoo is that it's source based and there are no (or few like lunar with very little community support (at least I think it's that way)) other distributions like that. I like Linux Mint very much but it's something like a finished product like apple/microsoft etc what I definitely don't like. And even so gentoo is not worse than those (in the "programming environment/text editing/youtube/multimedia etc" sense).

IMO it's absolutely not understandable to criticize gentoo and I consider it as "the only true OS " and I want to use it for everything (and do use it for everything, at least now) like learning/understanding linux, or more generally computer systems, and for working (programming, writing texts etc), day2day stuff and so on..

Are there any serious critics that I'm not aware ? And what do you think about those things?

Will a few threads and someone's old opinion on Gentoo change your own opinion? Especially if those are just claims based on experience from years long past, requests for experimental features and people thinking Gentoo will be always the same despite the OSS world changing rapidly. I think if you look at this stuff in retrospect, it shows that Gentoo has battled many issues that otherwise no other distro could have revealed and hence fixed many bugs, the developer don't just add experimental features without proper reasoning and that even though the OSS ecosystem (at least in the case of the base system) appears to be heavier these days, Gentoo can still stay clear of that within limits.

Make up your own opinion, don't let someone's opinion on something irrelevant to your use case change it. If Gentoo suits your needs, then use it. That's all.

Are there any serious critics that I'm not aware ? And what do you think about those things?

Even if there were severe critics they have long been addressed. There is a USE flag "vanilla" in rxvt-unicode which will install urxvt as provided by upstream. It is turned on by default._________________emerge --quiet redefined | E17 vids: I, II | Now using e17 | e18, e19, and kde4 sucks :-/